This work focuses on the oxidation of tungsten in inert gas atmospheres containing oxygen and moisture. It is particularly relevant for the European Spallation Source where the tungsten target is cooled by purified helium gas and the 5 MW proton beam can raise the maximum target temperature beyond the threshold for oxidation. Tungsten discs were oxidized isothermally at 400° to 900 °C for 2 h in pure helium and helium mixed with oxygen and water vapor, with varying partial pressures up to 500 Pa. Tungsten was oxidized even with a small amount of oxygen (≤5 ppm) present in industrially pure helium. Non-isothermal oxidation of tungsten foils was carried out in water vapor (∼100 Pa), in situ in an environmental scanning electron microscope. On specimens oxidized in inert gas containing water vapor (2 h, $p_{H_{2}O}$ ∼790 Pa), Auger electron spectroscopy studies confirmed the presence of a thin oxide layer (40 nm) at 400 °C. At 500 °C the oxide layer was 10 times thicker. A dark, thin and adherent oxide layer was observed below 600 °C. Above this temperature, the growth rate increased substantially and the oxide layer was greenish, thick and porous. Oxide layers with varying stoichiometry were observed, ranging from WO₃ at the surface to WO₂ at the metal-oxide interface. For comparison, oxidation of tungsten alloys in He-5%O₂ was studied. The implications of this work on the design and operation of the helium loop for cooling the target are discussed.

这项工作的重点是在含有氧气和水分的惰性气体气氛中氧化钨。对于欧洲散裂源尤其重要，在该处，钨靶材被纯净的氦气冷却，而5兆瓦的质子束可将最大靶材温度提高到超过氧化阈值。钨圆盘在纯氦气中和氦气中与氧气和水蒸气混合，在400°至900°C的温度下等温氧化2小时，分压高达500 Pa。即使少量的氧气（≤5ppm），钨也会被氧化）存在于工业纯氦中。钨箔的非等温氧化是在水蒸气（〜100 Pa）中，在环境扫描电子显微镜中原位进行的。在含有水蒸气的惰性气体中氧化的样品（2小时，$p_{H_{\mathrm{2个}}Ø}$约790 Pa），俄歇电子能谱研究证实在400°C下存在薄氧化层（40 nm）。在500℃下，氧化物层厚10倍。在600°C以下观察到深色，薄而粘着的氧化物层。高于该温度，生长速率显着增加，并且氧化物层发绿，厚实且多孔。观察到具有变化的化学计量的氧化物层，其范围从表面的WO ₃到金属-氧化物界面的WO ₂。为了比较，研究了钨合金在He-5％O ₂中的氧化。讨论了这项工作对冷却靶材的氦气回路的设计和运行的影响。